Bearing Interference - Preload formula

[SGEngineer]

I'm involved in a project whereby I'm trying to determine appropriate ball bearings for my design. Here's how it works:

The bearings are spaced evenly in a radial manner and are "squeezed" between a tube ID and a rod OD. The bearings preload establish good contact and prevent slipping while the rod is actuating.
The parts are of 63 microinch Ra and of hardened 440C SST HRc 58.

I've got a few questions on this topic.

1. What would be a good interference to preload the bearings so that they don't slip?
2. How do I establish the formula for relating preload to interference?
3. How much preload is required so as not to create any sliding effect on the bearings?

 

[Tmoose]

Why do you need to avoid slipping of the balls/rollers. Depending on radial load, commercially available wavy bearing preload springs provide ~ light preload, which is sufficient for light to modest radial load.

The relationship of axial motion (spacer offset)to preload force is complex and varies with size and style of bearing.
For 15 degree angular contact bearings up to 4 inch bore the per bearing "offset" to achieve light preload is likely to 0.001 inch or less. Making spacers with length controlled to 0.0001s is a challenge. WIth typical non-precision deep groove and ang contact bearings the width and face positions are not controlled well enough to allow clamping the bearings

 

[SGEngineer]

Hi Tmoose,

There's two reasons I need to avoid slippage.
1. Minimize wear on surfaces.
2. I need the bearings to lift a retainer (.1 lb max) up at constant speed.

I have precise machining on the bores and rods (.00001" bilateral), so that's not an issue. There would not be any grooves as the bearings are supposed to roll in almost all directions around the bore. The bearings size range from .1874" to .1876".

I know that it's complex relationship and to establish preload force to bearing size (to obtain interferences / clamping), we'll be expecting a non-linear equation. Just would like to know if there's anyone out there with such experience on doing this.